Abstract #M297

# M297
Increasing the concentration of linolenic acid in diets fed to Jersey cows in late lactation does not affect methane production.
J. V. Judy*1, T. M. Brown-Brandl2, S. C. Fernando1, P. J. Kononoff1, 1University of Nebraska-Lincoln, Lincoln, NE, 2USDA, ARS, US Meat Animal Research Center, Clay Center, NE.

Although the inclusion of fat has shown to reduce methane production in ruminants, relatively little research has been conducted on comparing the source and profile of fatty acids on methane production in lactating dairy cows. A study using 8 multiparous (325 ± 17 DIM) (mean ± SD) lactating Jersey cows was conducted to determine effects of feeding canola/tallow vs. extruded byproduct containing flaxseed as a fat source on methane emissions and diet digestibility in late lactation dairy cows. A crossover design with 35 d periods (28 d adaption and 7 d collections) was used to compare 2 different fat sources. Diets contained approximately 50% forage mixture of corn silage, alfalfa hay, and brome hay with only the concentrate mixture changing between diets to include either 1) a conventional corn/soybean meal/canola meal with tallow, or 2) a conventional corn/soybean meal diet with an extruded byproduct containing flaxseed (EXF) as the fat source. Diets were balanced to decrease corn and canola meal and replace them with EXF to increase linolenic acid supply (31.2 vs 201.6 g/d) to the rumen. Methane production was measured using headbox-style indirect calorimeters. Milk production was similar (P = 0.38; 17.4 ± 1.04 kg/d) as well as DMI (P = 0.26; 15.4 ± 0.71 kg/d) across treatments. Milk fat was similar (P = 0.87; 5.88 ± 0.25%) and milk protein (P = 0.69; 4.08 ± 0.14%) across treatments. For methane, production was similar (P = 0.90) for total production (352.0 vs. 349.8 ± 16.43 L/d for CM vs. EXF, respectively). Methane production per unit of DMI was similar (P = 0.34) and averaged 10.5 ± 0.57 L/kg. Similarly, methane production per unit of energy corrected milk was similar (P = 0.30) for fat source and averaged 7.01 ± 0.68 L/kg. Heat production was similar (P = 0.98) averaging 21.1 ± 1.02 Mcal/d. Digestibility of NDF, CP, DM, OM, and starch were similar (P ≥ 0.22) by diet and averaged 53.6, 73.3, 67.5, 69.9 and 96.1 for NDF, CP, DM, OM, and starch, respectively. Results indicate that increasing C18:3 may not affect methane emissions or digestibility of the diet.

Key Words: linolenic acid, methane, milk